1. Field of the Invention
The present invention relates to isomeric nonyl benzoates, processes for their preparation, mixtures of the same with alkyl phthalates, alkyl adipates, or alkyl cyclohexanedicarboxylates, and also to the use of these mixtures.
2. Related Art of the Invention
Polyvinyl chloride (PVC) is one of the most commercially important polymers. It has a wide variety of uses both in the form of unplasticized PVC and in the form of plasticized PVC. To produce a plasticized PVC, plasticizers are added to the PVC. Examples of such plasticizers include phthalates such as di-2-ethylhexyl phthalate (DEHP), diisononyl phthalate (DINP), and diisodecyl phthalate (DIDP). As the chain length of the esters increases within such plasticizers, the solvation or gelation temperatures rise and the processing temperatures of the plasticized PVC rise.
The processing temperatures can be reduced by adding what are known as fast fusing plasticizers. Examples of such fast fusers are the short-chain phthalates, dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), benzyl butyl phthalate (BBP), and diisoheptyl phthalate (DIHP). Moreover, dibenzoates, such as dipropylene glycol dibenzoates, or the like, may be used for the same purpose.
Due to their high solvating power, the presence of these fast fusers may lead to a marked rise in viscosity with time in PVC plastisols. In many cases, this has to be compensated by adding viscosity reducers which are often expensive.
A general demand during the preparation and processing of PVC plastisols is low viscosity and minimum gelation temperature. Another desirable feature of plastisol is a high shelf life which may be attributed to little increase in viscosity with time. High viscosity may be disadvantageous during processing of the plastisol in machinery. Further, an excessively high gelation temperature may lead to discoloration due to thermal stress.
There are only a few known plasticizers that provide a significant lowering of the gelation temperature in formulations and simultaneously maintain the viscosity of the plastisol at a low level, much less after storage for a period of some days. 2-Ethylhexyl benzoate has recently been proposed as a product which could provide these benefits [Bohnert, Stanhope, J. Vinyl Addit. Technol. (2000), 6(3), 146-149]. However, this compound has comparatively high vapor pressure, which leads to unacceptable losses of this compound during processing.
DE 19 62 500 discloses the use of a mixture of relatively long-chain esters of benzoic and phthalic acid for preparing plastisols. 3,5,5-Trimethylhexanol is preferably used for preparing the benzoates. No precise information is given concerning the phthalic diesters that may be used.
The use of phthalates whose ester groups have from 1 to 8 carbon atoms is more and more restricted due to toxicological reasons. Further, esters having relatively long alkyl side chains are classified as less toxicologically hazardous, but have poorer processing properties.